UNITED STATES MINERAL RESOURCES 



PHOSPHATE DEPOSITS 



By James B. Cathcart and R. A. Gulbiiandsen 



CONTENTS 



Page 



Abstract of conclusions 515 



Introduction 515 



Exploitation 516 



Geochemistry 517 



Types of deposits 517 



Igneous apatites 517 



Guano and related deposits 518 



Sedimentary phosphorite 518 



Deposits caused by divergence upwelling of 



sea water 518 



Deposits formed in warm currents along 



eastern coasts 519 



Deposits formed on stable shelves or in con- 

 tinental interiors 519 



Concentration and enrichment of marine de- 

 posits 520 



Other types of phosphate deposits 520 



Resources 520 



Identified and hypothetical resources 520 



Sedimentary phosphorite 520 



United States 520 



Latin America 522 



Africa and the Near East 522 



Asia 522 



Australia 522 



Guano and related deposits 522 



Igneous apatites 522 



Speculative resources 522 



Prospecting techniques 523 



Problems for research 523 



Selected bibliography 525 



105. 

 106. 



TABLES 



Marketed production of phosphate rock in the 

 United States in each 10th year of the period 

 1870 to 1970, and total production through 

 1971 



Phosphate resources of the United States 



World phosphate resources 



517 

 521 

 521 



ABSTRACT OF CONCLUSIONS 



Phosphorus, an element essential to plant growth, is found 

 in igneous apatite, guano or related deposits, and marine 

 phosphorite. Most of the United States' and the world's 

 reserves and resources are in the marine phosphorite de- 

 posits which also account for about 75 percent of the total 

 production. 



Marine phosphorite deposits, known throughout the world 

 in rocks ranging in age from Precambrian to Holocene, 

 form in basins away from sources of abundant clastic ma- 

 terial in warm latitudes in areas of upwelling water. 



Because most of the sedimentary basins are known and 

 phosphate occurs in many of them, resources are classed as 

 identified or as hypothetical. Speculative resources form only 

 a minor part of the total. However, identified resources of 

 the world are measured in billions of tons of contained 

 phosphorus and hypothetical resources are probably many 

 times as great. 



A major factor of concern is the transportation of a bulk, 

 low-value product to areas of use. Many problems, however, 

 remain to be solved, particularly in the accurate delineation 

 of reserves in the large areas of probable hypothetical re- 

 sources and in the mining and beneficiation of deeply buried 

 and low-grade resources. 



Environmental problems attendant upon open-pit mining 

 and chemical processing must be solved. Failure to solve 

 these problems in the United States may lead to drastic 

 changes in the traditional supply patterns of phosphate rock 

 in the world. 



Phosphate rock contains abundant fluorine and potentially 

 economically recoverable amounts of vanadium, uranium, 

 and the rare earths. Trace metals necessary to plant growth, 

 such as boron, copper, molybdenum, manganese, and zinc are 

 present in phosphate rock, are removed during chemical 

 processing, and are readded to make a complete fertilizer. 

 Chemical research on problems of recovery of minor elements 

 and the retention in chemical fertilizer of the trace metals 

 is needed. 



INTRODUCTION 



Phosphorus is one of the three elements vital to 

 plant growth, but it tends to be less abundant than 

 the other two (nitrogen and potassium) , particularly 

 in soils that have been extensively cropped or in 

 tropical soils that are thoroughly leached by acid 

 ground water. 



U.S. GEOL. SURVEY PROF. PAPER 820 



616 



